A test for comparing the means of two samples, or the mean of one sample (or even parameter estimates) with a specified value; also known as the "Student t-test" after the pseudonym of its inventor.

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64 views

t test with log transformation

One of my variables to be compared in a t-test is normally distributed, while the other is non-normally distributed. What test should I use? I thought I should do a reflect log10 transformation on the ...
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1answer
14 views

Correction of mutliple paired samples t-test

In one group of subjects I have four parameters (for e.g. A, B, C, D) measured in two conditions. I want to know whether these 4 parameters differ between the conditions by doing paired samples ...
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18 views

T-test to check a significance

Is it okay to perform independent sample T-test to test the effect of an health awareness intervention on male and female population registered at 300 polling booths in a town.
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1answer
21 views

Reporting degrees of freedom for Welch t-test

The Welch t-test for unequal variances (also known as Welch–Satterthwaite or Welch-Aspin) generally has a non-integer degrees of freedom. How should these degrees of freedom be quoted when reporting ...
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1answer
33 views

Difference between two measures

A numerical value was generated for each of 65 samples on machine A at time T, and then on machine B and time S. I tested for a difference between the two runs using R as follows: ...
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6 views

Balance checking in randomized controlled trials with large sample

I have a survey experiment in which the treated group receives a certain prompt that the control group does not. I also have a bunch of demographic variables that I want to check for balance between ...
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0answers
7 views

Compare model performance to distinguish two groups

I would like to compare a sample from the normal population NP to a sample from an "abnormal" population AP. I have several variables measured on both NP and AP, say age, gender, and VAR1, VAR2 and ...
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26 views

lay stats question

I am comparing two prospective observational cohorts; the "study group" (n=30) has undergone previous intervention that "failed" and has undergone a 2nd intervention. This is being compared with a ...
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0answers
14 views

Upper bound for sampling fraction for CLT to hold

What is the upper bound for the sampling fraction for the Central limit theorem to hold when sampling without replacement? Context The context for my question is that it is regularly argued (see e.g. ...
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34 views

White noise test interpretation

How to interpret white noise test from Stata? Have a white noise means that a variable does not have autocorrelation. Can I say here that all of my variables has a white noise (does not have ...
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1answer
43 views

Modeling within subjects

I am having a bit of a statistics problem, and thought I would throw it to the internet before I bash my head in. Participants were shown stimuli and asked a question while EEG was recorded. The ...
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2answers
59 views

Which test to use when t-test is not apropriate?

I have two groups, male and female teachers. I want to see if there is a statistically significant difference in mean pay. There are 48 male teachers, which is enough to use a t-test. However, there ...
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1answer
54 views

ANOVA or ANCOVA

I have to analyze a study where 2 treatments (t1 and t2) were used to control blood sugar levels. The 't2' is a new treatment which is being compared with an old established treatment 't1'. I have a ...
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13 views

T test as Mahalanobis distance

Our tutor once said that T test applies Mahalanobis distance (hope I've heard it right). Could you please explain, how it does so? Denis
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21 views

ARIMA, coefficients check

I would appreciate if someone could check the mathematical equation for the seasonal ARIMA (4,1,3) x (1,1,1) period 12 that I wrote. I have done it this way, but I am not really sure if it correct is. ...
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0answers
14 views

Compare two populations by their means… t-test?

I would like to have your opinion on the best way to compare two small sized populations of 13 and 14 individuals (but I have 3 tests for each individual on my dataset, so should I use 13 and 14 or 39 ...
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1answer
26 views

Compare means of two (contentwise) different variables

I have a question about comparing the means of two variables that have a different meaning but a (possibly) similar ways of measuring them. To give an example: Let's say I am conducting a study in ...
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10 views

Is this estimator for the standard error of a sample mean difference biased and what is the relation to Student's t-test?

In the situation of two indepdent samples, the variance of the difference in sample means $\bar{x}_1$ and $\bar{x}_2$ is $$Var(\bar{x}_d)=\frac{\sigma_1^2}{n_1}+\frac{\sigma_2^2}{n_2}=\sigma_d^2$$ and ...
2
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1answer
25 views

Paired difference test for nonhomogenous variances

Concrete scenario: A random sample of adults in Idaho rate each of 'kombucha', 'apple juice' and 'grape juice' on a scale from 0 to 1. Does the population of Idaho assign significantly different mean ...
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23 views

Significant difference within line set and between two sets of lines

For my research a person has walked on a treadmill which contains two pressure plates: One below the left foot, one below the right. I would like to compare the force in the z (downwards) direction ...
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1answer
15 views

Can two samples of 189 and 50 undergo independent samples t test?

I have taken two types of subjects related to two categories one has a sample size of 189 and other has 50...Can I apply independent samples T test on them ????
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9 views

On computing the Wolfe's t-Test

I have a sample with $n=1000$ subjects. For each subject I have three variables measured, let's say $X$, $Y$ and $Z$. I have the following correlations: $r_{xz}$ = 0.80 $r_{yz}$ = 0.83 I want to ...
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1answer
31 views

Probabilistic comparison of two mixture models?

Given two gaussian mixture models (GMMs) with different degrees of freedom, is there a way to determine the probability that one is generated from the other? That is, can we give a probability to the ...
4
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1answer
44 views

When does an unpaired test result in higher p-value than a paired test?

I determined some parameter in a group of subjects under two conditions, such that each subject was tested in both conditions. I want to know if the condition has an effect on the parameter. My design ...
2
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1answer
46 views

Asymptotic distribution of a recursive statistic

I have a (time series related) test statistic which is asymptotically normal. I would like to know what is the asymptotic distribution of its maximal value obtained by a recursive estimation. For ...
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1answer
35 views

Statistical test of stock returns product

Say I have a sequence of stock returns: $X_1, ..., X_n$. Then I make a sample of products: $X_1X_2, X_2X_3, ..., X_iX_{i+1},..., X_{n-1}X_n$ How to test, if the sample mean is significantly different ...
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38 views

Advice on research study

I am collecting data on extroversion using a personality scale at a clinic. I have about 50 subjects where 15 are in experimental group receiving interventions. I am also collecting data on ...
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18 views

Using t-test for feature selection after z-scoring data?

Suppose I have a high-dimensional dataset, and a binary classification problem. I want to use the two-sample t-test for feature selection. If the data has been normalized by z-scoring (so it has zero ...
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1answer
18 views

power to detect effect sizes for the usual t, Welch Adjusted t, and Mann-Whitney U test

For class, I am given a series of sample sizes and variances for two groups and am asked to calculate the power for detecting effect sizes for the usual t test, Welch adjusted T test, and the ...
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34 views

Statistical test: Does actual time series data deviate from forecast?

I have made a prediction of future sales based on an ARIMA model. The ARIMA model is based on past data, during which there has been no marketing activity. During the period predicted by ARIMA, I will ...
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0answers
21 views

A/B testing zero inflated data

I am trying to conduct an A/B(/C) test to compare the performance of 3 different website pages but I'm facing issues regarding zero inflated data. I have data for each page regarding ...
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1answer
68 views

Best way to compare pre vs post levels in treatment vs control groups?

In a study, drug was given to tt (treatment) group and not to cc (control) group and blood levels of (say) cholesterol were tested before and after in each subject. I have following data: ...
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2answers
34 views

p-value test for comparing classifiers

I have to use p-value test to compare two classifiers. I am getting the error vectors of 2 hypothesis and I am using their difference as an input in ttest function of MATLAB ...
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1answer
20 views

math explanation for using paired-t

Not a math/stats person, but I am interested in finding out why "paired t" would be a preferred test for samples that are not "independent". I googled a bit on this topic, but didn't really find ...
0
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1answer
54 views

Calcuate Bayes Factor for Adjusted Mean Difference

I have an ANCOVA model shown below (fit) where I calculated the mean difference between two groups while controlling for another variable (x). For the adjusted mean difference (288.72), I'd like to ...
3
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1answer
43 views

Independent/Dependent variables & type of statistical test

If someone is investigating differences in means between 2 groups, does it matter which we consider to be the IV and the DV? For example, can I use a t test to examine the difference in the age of ...
2
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1answer
36 views

hypothesis test for a boolean combination of alternatives

I have a student (for a high school project) who has conducted an experiment and collected data in the following (simplified) way: id|situation|scoreX|scoreY ...
3
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2answers
38 views

Is paired t test sufficient to show the two data sets are similar

Let me give the details of my problem setting, we have a learning algorithm that can take a collection of algebra problems and automatically generate similar ones. Of course, an important question to ...
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0answers
8 views

Comparing two sample means (t-test) [duplicate]

In a t-test of two sample means, with 2 degrees of freedom, the t-stat = -14.55. The two-tail significance is 4.30. My question is, is the t-stat significant? And, the t-stat seems to be ...
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0answers
13 views

comparison of time values as response variable

The data set I have is a 12 subject Latin Square cross-over design with 2 periods (1 or 2), 2 sequences (AB OR BA) and 2 drug formulation treatments (A or B). The subject response variable is a time ...
3
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46 views

Which statistical test for women height?

Suppose women may have Blue or Red eyes. We make a first cheap research on a 100 women checking just one eye of each woman. So after the research we have results: At least one eye Blue have avg ...
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1answer
49 views

How to describe three groups where the means of two groups are significantly different, but neither of the two groups differ from a third group?

I am comparing 3 means from normal distributions using student's test: $\mu{_1}, \mu{_2}, \mu{_3}$ Results are: $\mu{_1} = \mu{_2}, \mu{_2} = \mu{_3}, \mu{_1} \ne \mu{_3} $ If I want to group my ...
2
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1answer
33 views

Testing if a interval scaled variable A and a nominally scaled variable B are independet when A is not normally distributed

We have a variable A which denotes a percentage between 0 and 1. The variable is not normally distributed but has a very left skewed distribution. About 5% of the observations are zero, most ...
2
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3answers
71 views

Can I do a t-test to test significance? [closed]

I need a statistical test to determine if one group of ten classrooms with different numbers of students in each class has a class average on a test. Group two has 12 classrooms also with different ...
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1answer
32 views

Is this a case of multiple-test?

I had a different view with a friend on whether we need an adjustment of p.values for multiple tests. Here is the case, we have a compositional data set with $n=1000$ subjects and $m=26$ continuous ...
3
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2answers
70 views

Empirical rejection rate of a wrong null hypothesis -is it the “power of the test”?

I guess this is basic, but it forms part of the holes in my statistics education. What I know is that the power of a hypothesis test is not a fixed magnitude, but a function of various factors ...
0
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1answer
53 views

Using 2 sample T test in time series data

I have two data series (not stationary) and I would like to see if the mean of series 1 is significantly different when a certain condition (on the other series) is met. The theory is that when ...
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2answers
73 views

Hypothesis testing: difference between proportions

I am investigating staff inequality between genders and ethnicities in an institution. I have data on contract types (permanent or fixed term) and pay grades for almost all employees. I want to test ...
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0answers
18 views

Degrees of freedom for a t-test using multiple imputation

I ran a paired samples t-test using multiple imputation in SPSS, and I am unsure as to how to proceed in reporting the degrees of freedom from the pooled data. The original data had 43 df and now it ...
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346 views

Calculate at .05 level of significance

A research organization claims that the monthly wages of industrial workers in district X exceed those in district Y by more than Rs 150. Two different samples drawn independently from the two ...